Light getting through reservoir question

So I'm putting together my own Ebb and gro system and got a great deal on this drum for $35. It's blue no big deal, but then i thought about light getting through it. I held a bright LED flashlight next to it and sure can see it through. I'm not against spending another $10 on spray paint to make it black.

So I was just wondering if:
A. anyone knows should i definitely paint it to prevent 100% of the light?
B. its going to be far enough away from the light on the ceiling (400w) that nothing will be able to grow in it anyway.

Here's some quick pics.

One holding the flashlight right up to the side.
 
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